This volume is the most recent and over-arching contribution of B. to a prolific body of publications. Best known for his work on the northern British frontiers, principally Hadrian's Wall and the Antonine Wall, B. now presents a general synopsis and understanding of the Roman empire's frontiers based on a lifetime of studying the limites.

The book is separated into three parts and twenty chapters, sandwiched by a short introduction and brief conclusion. Part 1 consists of a review of the concept and definition of frontiers and an overview of the sources, textual and archaeological, presented chronologically and thematically. Part 2 examines the different ‘types’ of frontiers, distinguished by B. relative to form (e.g. linear) or environment (e.g. river, desert, mountain, sea, forests, marshes and swamps), concluding with a concise assessment of the concept of defence-in-depth. Part 3 separates brief thematic essays on interpretation, considering the development of frontiers, military deployment, comparison of frontiers, decision making, how frontiers worked, and the purpose and operation of frontiers, and finishes by addressing the success of imperial frontiers. Each chapter is relatively short, and the book is well served by numerous illustrations in greyscale, primarily consisting of maps and site plans. A short section of colour plates is useful in conveying the range of landscapes found in the frontiers. The front matter includes a note on technical usage (measurements, dates, etc.) and a select list of Roman emperors, their regnal dates and separation of dynasties. Following the conclusions is a selection of suggested reading, thematically organised, followed by a summary of sites to see in each country, chapter endnotes and an index.

The book is published by Pen & Sword, and thus it is intended for a wider public audience rather than for purely academic consumption. It is important to remember this, as it has informed the structure and language of the volume – to its benefit. B. makes direct arguments in plain English, and this makes the book both widely accessible and expedient to use. The collation of texts and inscriptions in thematic chapters will prove useful for students and researchers alike, and the inclusion of archaeological sites that are not commonly known is another benefit. The maps have been created by K. Schaller (University of Salzburg) to a consistent standard, facilitating reader interpretation and understanding. B. presents an archaeological account of Roman frontiers, drawing on texts and inscriptions, but with weight given to material evidence and remains. Thus, topography, landscape and the distribution of military installations are more instrumental in B.'s articulation of the concept and definition of the frontier than references to ancient writers on politics, cosmology or history.

The brevity of the chapters is deceptive. While these present quick thrusts tightly focussed on a given topic, the whole is more than the sum of its parts and this book will be a standard reference for frontier studies. Part 2 is largely descriptive and chronological in its treatment of the various frontiers, but the separation of frontiers by their primary form or underlying climate and topography provides an interesting clustering of various areas that is not strictly geographical in its presentation. This has the benefit of placing two geographically separated frontiers in the empire in succession in the text, making the similarities and differences more clearly apparent in the discussion at the end of each chapter.

Part 3, ‘Interpretation’, is where the core of B.'s arguments can be found, and this section can be seen as a consideration of the function of frontiers through various strands. Chapters 15 and 16 examine military deployment and compare the frontiers, respectively, but both indicate the importance of topography and logistics as they relate to people both friendly and hostile. Chapter 17 reminds us of the political and military hierarchy in which any frontier activities must be framed, and Chapters 18 and 19 look at how frontiers worked. A strong theme throughout these chapters is Roman assertion of control – achieved through political/diplomatic and economic means across the frontiers, and through military force employed for direct control of the landscape defensively and offensively. Legions and field armies were placed for defence of the empire against invaders, with auxiliaries and frontier units intended to hinder and prevent raiding, while also controlling movement into and out of the empire (p. 205). Chapter 19 further advances the debate of function, often centred on Hadrian's Wall. Linear frontier works, in particular, combine the defensive role of soldiers with a need to control movement across a landscape where natural obstacles are lacking. In essence, the ‘purpose of Roman frontiers can be summed up in one word: security’ (ibid.). The focus on security and control incorporates defence concerns while also accepting that the complexity of the situation on the ground cannot be reduced to defence alone. This is to be applauded, but has to be conditioned with one criticism. While the concern with defence against barbarian raiders and invaders is acknowledged throughout the text with reference to raiding and skirmishing, there is no explicit discussion of the scale or nature of threats relative to each frontier. The relative threat of barbarian groups is not easy to assess, but its absence is conspicuous due to the wide-ranging coverage and synthetic nature of the book that so clearly draws out the similarities and contrasts between frontiers.

B. has provided an invaluable contribution to Roman frontier studies that offers a more archaeological interpretation, contrasting with the more influential work by ancient historians over the past fifteen years. The argument is presented clearly in an accessible fashion, with endnotes guiding those with further interest and enquiries. The chronological range is more balanced than many general frontier studies, and the text is well supported by maps, plans, reconstruction drawings and plates. The distinct separation of frontiers by topography and climate rather than the traditional geographic identification proves to be an illuminating exercise. The succinct and clear text will make this book a favourite of students and frontier specialists alike.